1. Field of the Art
This invention relates to a catheter type ultrasound probe with an ultrasound observation means incorporated into a tip end section of a catheter member to be introduced into an intracavitary portion for examination or other purposes.
2. Prior Art
Ultrasound examination systems are generally arranged to transmit ultrasound pulses toward a target portion through an intracavitary wall by driving an ultrasound transducer while receiving and processing return echo signals to display tomographic ultrasound images on a monitor screen. In this regard, there have been known in the art the so-called catheter type ultrasound probes which have an ultrasound transducer at the tip end of a flexible catheter member to be introduced into an intracavitary portion of interest. Some of such catheter type ultrasound probes are tailored to secure a view field of ultrasound image by means of a B mode ultrasound scanning system adapted for a linear or convex scanning operation with an ultrasound transducer under either mechanical or electronic drive. For example, in case of electronic linear or convex scanning operations, it is the usual practice to use a catheter member which has a plural number of ultrasound transducer elements arrayed axially in a row on its rigid tip end portion, driving the ultrasound transducer elements sequentially under electronic control to produce an ultrasound image over a predetermined view field.
When a diseased portion is spotted by an ultrasound examination, there often arises a need for penetrating a puncture needle into the diseased portion for injection of medicine or contrast medium, for sampling tissues or for drainage. The puncture needles which serve for these purposes generally has a hollow needle body with a sharp pointed end for penetration to an aimed depth of an intracorporeal portion. Such a puncturing operation is monitored through ultrasound images on a monitor screen to guide the needle point to a diseased portion or other locality which needs a treatment. The puncture needle of this sort is formed of a rigid pipe at least in its fore end portion to ensure smooth penetration into target intracorporeal portions.
In this connection, in case the ultrasound transducer consists of a plural number of transducer elements which are arrayed axially on a catheter member as mentioned hereinbefore, the catheter member necessarily needs to have a rigid fore end section which is axially elongated to support the transducer elements thereon. A problem with such a catheter member is the difficulty which is invariably encountered in passing the lengthy rigid fore end section through an angularly bent portion in an intracavitary path of insertion of the catheter member, for example, in inserting same into the esophagus around the angularly bent throat portion. Difficulties are also encountered in turning the rigid fore end section toward a particular direction within an intracavitary portion or in turning the active face of the ultrasound transducer closely toward a particular target portion of ultrasound examination. Further, for the purpose of monitoring the puncturing operation by way of ultrasound images under observation, it is necessary to launch the puncture needle from a position close to the ultrasound transducer and at a predetermined angle with the face of the ultrasound transducer, for example, at an angle of 30.degree., so that the needle point of a rigid pipe should fall within the view field of the ultrasound image under observation. This gives rise to another problem that it is extremely difficult to launch a rigid pipe puncture needle at such a large angle through a needle guide passage which runs axially through the catheter member and turns its direction acutely toward a needle exit opened on a lateral side of the rigid fore end section of the catheter member closely on the near side of the ultrasound transducer.